The present invention relates to a self-piercing rivet in the form of a semihollow self-piercing rivet or full hollow self-piercing rivet for producing a self-piercing rivet joint between two or more metal sheets.
Self-piercing riveting as a joining method has gained increasing importance in the recent past. One important parameter for the joining operation as well as the joining quality of the self-piercing rivet joint is the geometry of the self-piercing rivet. In the state of the art numerous different geometries of the self-piercing rivet are known, see e.g. EP 0 720 695, EP 1 064 466, EP 1 229 254, EP 1 387 093, DE 44 31 769, DE 203 19 610 U1, DE 200 01 103 U1, US 2004/0068854 A1, JP 2001159409A, JP 09317730A et alia.
The self-piercing rivet according to the above named EP 0 720 695, which is normally described as a C rivet, is used on a large scale in the motor vehicle industry, but also in other technical fields. This is a semihollow self-piercing rivet with a rivet head and a rivet shank with a central shank borehole of which the rivet head has a plane top side and a cylindrical head exterior and the rivet shank has a cylindrical shank exterior and a cylindrical shank interior confining the central shank borehole. The cylindrical head exterior and the cylindrical shank exterior are directly joined to each other through a relatively large radius. In the bottom region of the self-piercing rivet the central shank hole is formed as a cone, wherein the cone flanks are supposed to be slightly curved according to the specifications in this publication. As a result of this within the framework of the given production engineering possibilities a kind of “sharp edge” is prepared on the of the rivet shank, which in practice is generally somewhat chamfered. According to the specifications in this publication the opening angle of the cone can range between 25° and 120°.
Even though the C rivet has proved to be successful in practice, it comes up against limiting factors in particular in the case of self-piercing riveting high strength sheet steel.
Thus for example an improvement with regard to the achievable joint quality and load bearing capacity of the self-piercing rivet joint, stress of the rivet during the joining operation, and gap formation between the rivet and the metal sheets would be desirable.